A ballast water treatment plant has operated on the south shore of Port Valdez, Alaska since 1977. In recent years the plant processed, on the average, nearly 51,000 m**3 of the ballast water per day. Since the plant operations began, total hydrocarbon concentrations (THC) in the port sediments have increased to over 200 ug/g dry weight. In the mussel Mytilus edulis and the clam Macoma balthica collected near the effluent diffuser, total hydrocarbon concentrations are over 400 ug/g dry weight. Increased concentrations of polycyclic aromatic hydrocarbons (PAH's) and hopanes strongly suggest the petrogenic nature of the added hydrocarbons. Additional study results are presented in the abstract. An environmental monitoring protocol requiring a priori criterion for biologically significant impact is suggested for the port.